If you go in and out of consciousness/sleep, you must ask your Rov/Posek if you are allowed to fast at all. He might refer to a doctor to determine if it is a medical issue. For example; There are many people who when they fast their blood pressure or glucose level bottoms out, especially those that suffer from Mitral Valve Prolapse. At that point their Rov/Posek might suggest eating with shiurim. ????? ?????.
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